Ive just set up some ppc ads in google for a gay adult video site (you know the type ) anyhows. After 2 days 90% of my keywords were decided to be 'great' and thus i could list them for just 0.05 a click. In the last 12 hours 95% of those keywords have now seen their quality score drop to OK or Poor. These are super targeted words such as 'free gay movies' 'download free gay movies' etc, exaclty what the site is about so why am i being told that my quality score is poor for these. I'm not prepared to increase my min bid to 0.50 for keywords which im the ONLY person advertising on that keyword!!
The initial CPC is always set to 0.05, sometimes a little more or less, but since its brand new the initial QS is high. As you start to get impressions and clicks, your QS is adjusted based on industry standards. If you are the only persons ads that are showing for your keywords when searched in google, then you may be in a market that is frowned upon by google and eventually be weeded out till bids are not worth the investment, or be turned off completely.